platelet count

platelet count The calculated number of platelets in a volume of blood, usually expressed as platelets per cubic millimeter (cmm) of whole blood. Platelets are the smallest cell-like structures in the blood and are important for blood clotting and plugging damaged blood vessels. Platelet counts are usually done by laboratory machines that also count other blood elements such as white and red cells. Platelets can also be counted with the help of a microscope. Normal platelet counts are in the range of 150,000 to 400,000 per microliter These values may vary slightly among different laboratories. See also CBC.